Manipulating Crystal Growth and Secondary Phase PbI2 to Enable Efficient and Stable Perovskite Solar Cells with Natural Additives.

In perovskite solar cells (PSCs), the inherent defects of perovskite film and the random distribution of excess lead iodide (PbI2) prevent the improvement of efficiency and stability. Herein, natural cellulose is used as the raw material to design a series of cellulose derivatives for perovskite crystallization engineering. The cationic cellulose derivative C-Im-CN with cyano-imidazolium (Im-CN) cation and chloride anion prominently promotes the crystallization process, grain growth, and directional orientation of perovskite. Meanwhile, excess PbI2 is transferred to the surface of perovskite grains or formed plate-like crystallites in local domains. These effects result in suppressing defect formation, decreasing grain boundaries, enhancing carrier extraction, inhibiting non-radiative recombination, and dramatically prolonging carrier lifetimes. Thus, the PSCs exhibit a high power conversion efficiency of 24.71%. Moreover, C-Im-CN has multiple interaction sites and polymer skeleton, so the unencapsulated PSCs maintain above 91.3% of their initial efficiencies after 3000 h of continuous operation in a conventional air atmosphere and have good stability under high humidity conditions. The utilization of biopolymers with excellent structure-designability to manage the perovskite opens a state-of-the-art avenue for manufacturing and improving PSCs.

Aggregation-regulated room-temperature phosphorescence materials with multi-mode emission, adjustable excitation-dependence and visible-light excitation.

Constructing room-temperature phosphorescent materials with multiple emission and special excitation modes is fascinating and challenging for practical applications. Herein, we demonstrate a facile and general strategy to obtain ecofriendly ultralong phosphorescent materials with multi-mode emission, adjustable excitation-dependence, and visible-light excitation using a single organic component, cellulose trimellitate. Based on the regulation of the aggregation state of anionic cellulose trimellitates, such as CBtCOONa, three types of phosphorescent materials with different emission modes are fabricated, including blue, green and color-tunable phosphorescent materials with a strong excitation-dependence. The separated molecularly-dispersed CBtCOONa exhibits blue phosphorescence while the aggregated CBtCOONa emits green phosphorescence; and the CBtCOONa with a coexistence state of single molecular chains and aggregates exhibits color-tunable phosphorescence depending on the excitation wavelength. Moreover, aggregated cellulose trimellitates demonstrate unique visible-light excitation phosphorescence, which emits green or yellow phosphorescence after turning off the visible light. The aggregation-regulated phenomenon provides a simple principle for designing the proof-of-concept and on-demand phosphorescent materials by using a single organic component. Owing to their excellent processability and environmental friendliness, the aforementioned cellulose-based phosphorescent materials are demonstrated as advanced phosphorescence inks to prepare various disposable complex anticounterfeiting patterns and information codes.

Seashell-Inspired Switchable Waterborne Coatings with Complete Biodegradability, Intrinsic Flame-Retardance, and High Transparency.

Inspired by the "brick-and-mortar" structure and the whole lifecycle eco-friendliness of seashells, we have constructed a proof-of-concept and environmentally friendly coating with switchable aqueous processability, complete biodegradability, intrinsic flame retardance, and high transparency, via using natural biomass and montmorillonite (MMT). We first designed and synthesized cationic cellulose derivatives (CCD) as the macromolecular surfactants, which effectively exfoliated MMT to obtain nano-MMT/CCD aqueous dispersions. Subsequently, via a simple spray-coating process and a post-treatment process with a salt aqueous solution, the transparent, hydrophobic, and flame-retardant coating was fabricated with a "brick-and-mortar" structure. The resultant coating exhibited an extremely low peak heat release rate (PHRR) of only 17.3 W/g, which is 6.3% of cellulose PHRR. Moreover, it formed a lamellar and porous structure once ignited. Thus, this coating could effectively protect combustible materials from fire. In addition, the coating had a high transparency (>90%) in the range of 400-800 nm. After use, the water-resistant coating was converted into a water-soluble material by using a hydrophilic salt aqueous solution, which then could be easily removed by water. Furthermore, the CCD/nano-MMT coating was completely degradable and nontoxic. Such a switchable and multifunctional coating with whole lifecycle environmental-friendliness exhibits huge application potential.

Cellulose-Based Ultralong Room-Temperature Phosphorescence Nanomaterials with Tunable Color and High Quantum Yield via Nano-Surface Confining Effect.

How to achieve multicolor organic room-temperature phosphorescence (RTP) is still challenging and striking. Herein, we discovered a new principle to construct eco-friendly color-tunable RTP nanomaterials based on the nano-surface confining effect. Cellulose nanocrystal (CNC) immobilized cellulose derivatives (CX) containing aromatic substituents via hydrogen-bonding interactions, which effectively inhibit the motion of cellulose chains and luminescent groups to suppress the nonradiative transitions. Meanwhile, CNC with a strong hydrogen-bonding network can isolate oxygen. CX with different aromatic substituents regulate the phosphorescent emission. After mixing CNC and CX directly, a series of polychromatic ultralong RTP nanomaterials were obtained. The RTP emission of the resultant CX@CNC can be finely adjusted through the introduction of various CX and the regulation of the CX/CNC ratio. Such a universal, facile, and effective strategy can be used to fabricate various colorful RTP materials with wide color gamut. Because of the complete biodegradability of cellulose, the multicolor phosphorescent CX@CNC nanomaterials can be used as eco-friendly security inks to fabricate disposable anticounterfeiting labels and information-storage patterns via conventional printing and writing processes.

Super-rapid and highly-efficient esterification of cellulose to achieve an accurate chromatographic analysis of its molecular weight.

Herein, a striking anion-tunnel transfer effect was demonstrated in 1-butyl-3-methylimidazolium benzoate (BmimPhCOO) ionic liquid, so a rapid, mild and efficient benzoylation of cellulose is accomplished under catalyst-free condition in BmimPhCOO. In a wide temperature range of 20-80 °C, the equilibrium of reaction is reached within only 15 min, which is much faster than the reported acylation of cellulose. Furthermore, the resultant cellulose tribenzoates have excellent solubility in conventional organic solvents, thus they can be used to accurately reflect the molecular weight and dispersity index of cellulose raw materials by gel permeation chromatography. This method is suitable for various cellulose. Therefore, we found a new principle to realize the extremely-rapid acylation of cellulose, and proposed an effective approach to accurately determine the molecular weight parameters of cellulose.

Ultralong phosphorescence cellulose with excellent anti-bacterial, water-resistant and ease-to-process performance.

Herein, we present a phosphorescent cationized cellulose derivative by simply introducing ionic structures, including cyanomethylimidazolium cations and chloride anions, into cellulose chains. The imidazolium cations with the cyano group and nitrogen element promote intersystem crossing. The cyano-containing cations, chloride anions and hydroxyl groups of cellulose form multiple hydrogen bonding interactions and electrostatic attraction interactions, effectively inhibiting the non-radiative transitions. The resultant cellulose-based RTP material is easily processed into phosphorescent films, fibers, coatings and patterns by using eco-friendly aqueous solution processing strategies. Furthermore, after we construct a cross-linking structure by adding a small amount of glutaraldehyde as the cross-linking agent, the as-fabricated phosphorescent patterns exhibit excellent antibacterial properties and water resistance. Therefore, considering the outstanding biodegradability and sustainability of cellulose materials, cellulose-based easy-to-process RTP materials can act as antibacterial, water-resistant, and eco-friendly phosphorescent patterns, coatings and bulk materials, which have enormous potential in advanced anti-counterfeiting, information encryption, disposable smart labels, etc.

Immobilization of Ionic Liquids with a New Cellulose Ester Containing Imidazolium Cation for High-Performance CO2 Separation Membranes.

CO2 gas separation is of significant importance to protect the environment and utilize the carbon resource. In this work, two kinds of new cellulose esters containing imidazolium cation, cellulose acetate (CA) 1-butyl-3-methylimidazolium chloride and CA 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (CA-BmimTf2 N), are designed and synthesized. The resultant cationized cellulose esters effectively lock various ionic liquids (ILs) via electrostatic interactions. Due to the strong attraction interactions, the obtained cellulose ester/ILs composite membranes are uniform, smooth, and highly transparent. Moreover, the added ILs with a long alkyl chain in the cation and a bis(trifluoromethane sulfonyl)imide anion remarkably improve the CO2 permeability of the cellulose ester/ILs membranes, because of the dramatic increase of the CO2 diffusion rate. The CA-BmimTf2 N/C10 mimTf2 N membranes exhibit the highest CO2 permeability, which is 3800% higher than that of CA membrane and 1700% higher than that of CA-BmimTf2 N membrane. More importantly, the CA-BmimTf2 N/C10 mimTf2 N membranes have good mechanical properties and thermal stability. Such high-performance CO2 separation membranes with high CO2 permeability, high transparency, and good mechanical property have a huge potential in the practical utilization for gas separation.

[Homogeneous synthesis of cellulose phenylcarbamates and evaluation of their enantioseparation capabilities].

Understanding the structure-property relationship of polysaccharide derivatives is of great significance toward the development of novel chiral stationary phases. In this work, we used an ionic liquid, 1-allyl-3-methylimidazolium chloride (AmimCl), as the solvent and introduced phenyl isocyanates with various substituents into cellulose to obtain a series of cellulose phenylcarbamates. The effects of the degree of substitution (DS), as well as the type and position of the substituents, on the chiral separation capability of the cellulose phenylcarbamates were researched in detail. With an increase in the DS, the chiral recognition capability of the cellulose phenylcarbamates improved dramatically for most of the chiral analytes. Fully substituted cellulose phenylcarbamates showed the best enantioseparation capabilities. In addition, the type and position of the substituents on the benzene ring significantly influenced the chiral separation capabilities of the cellulose phenylcarbamates. Cellulose 3-methyl-4-chlorophenylcarbamate, 3,5-dichlorophenylcarbamate, and 2-methyl-5-chlorophenylcarbamate had better chiral recognition capabilities than cellulose 3,5-dimethylphenylcarbamate for some chiral analytes.

Regioselectively substituted cellulose mixed esters synthesized by two-steps route to understand chiral recognition mechanism and fabricate high-performance chiral stationary phases.

It is challenging to design and fabricate new and high-performance cellulose-based chiral stationary phases (CSPs), due to the indistinct chiral recognition mechanism and the inherent difficulty to control the structure of cellulose derivatives. Herein, taking advantage of the high regioselective benzoylation of cellulose in 1-allyl-3-methylimidazolium chloride, a series of regioselectively substituted cellulose mixed esters, cellulose 6-benzoate-2,3-phenylcarbamate, are directly obtained by a facile two-steps route without protecting and deprotecting process. The resultant cellulose mixed esters exhibit high chiral recognition capability. In particular, when the benzoate group has an electron-donating substituent on phenyl ring, such as 4-tert-butyl group, the corresponding regioselectively substituted cellulose mixed esters have much better enantioseparation capability than cellulose tri(3,5-dimethylphenylcarbamate), which is commercially available as Chiralcel OD column, one of the most powerful CSPs. More importantly, via adjusting the chemical structure of cellulose derivatives and adding a post-treatment process to optimize their chiral recognition properties, the chiral recognition mechanism is clearly revealed. The synergy of the hydrophobic helical conformation, weak hydrogen-bond donating ability and appropriate distribution of substituents of cellulose derivatives is essential to fabricate high-performance CSPs.

Chemoprotective action of lotus seedpod procyanidins on oxidative stress in mice induced by extremely low-frequency electromagnetic field exposure.

With the increasing use of electromagnetic technology, the effects of extremely low-frequency electromagnetic fields (ELF-EMF) on biological systems, central neurotransmitter systems, and human health have attracted extensive attention worldwide. In this study, lotus seedpod procyanidins (LSPCs) were evaluated for their protective effects on ELF-EMF induced oxidative stress injury in mice. Sixty male ICR mice were used for the experiment. The mice were randomly divided into five equal groups. The control group did not receive LSPCs or ELF-EMF but orally received normal saline. The ELF-EMF group received ELF-EMF exposure plus normal saline orally. The other three groups received ELF-EMF exposure plus LSPCs orally (60, 90, or 120mg kg(-1).bw, respectively). Each group exposed to ELF-EMF at 8 mT, 4h day(-1) for 28 consecutive days after administration daily of LSPCs or normal saline to mice for 15 consecutive days with the exception of the control group. Thereafter, blood and cerebral cortex of the mice were analyzed for antioxidant indices, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione-S-transferase (GST) and malondialdehyde (MDA). LSPCs administration at different doses significantly inhibited oxidative stress damage of mice induced by ELF-EMF. LSPCs treatment augmented SOD, CAT, GSH-Px, GR and GST activity. Furthermore, administration significantly lowered MDA level in LSPCs treatment groups LSPCs. All results indicated LSPCs can effectively prevent oxidative stress injury induced by ELF-EMF exposure, which may be related to its ability of scavenging free radicals and stimulating antioxidant enzyme activity.

Neuroprotective effects of lotus seedpod procyanidins on extremely low frequency electromagnetic field-induced neurotoxicity in primary cultured hippocampal neurons.

The present study investigated the protective effects of lotus seedpod procyanidins (LSPCs) on extremely low frequency electromagnetic field (ELF-EMF)-induced neurotoxicity in primary cultured rat hippocampal neurons and the underlying molecular mechanism. The results of MTT, morphological observation, superoxide dismutase (SOD) and malondialdehyde (MDA) assays showed that compared with control, incubating neurons under ELF-EMF exposure significantly decreased cell viability and increased the number of apoptotic cells, whereas LSPCs evidently protected the hippocampal neurons against ELF-EMF-induced cell damage. Moreover, a certain concentration of LSPCs inhibited the elevation of intracellular reactive oxygen species (ROS) and Ca(2+) level, as well as prevented the disruption of mitochondrial membrane potential induced by ELF-EMF exposure. In addition, supplementation with LSPCs could alleviate DNA damage, block cell cycle arrest at S phase, and inhibit apoptosis and necrosis of hippocampal neurons under ELF-EMF exposure. Further study demonstrated that LSPCs up-regulated the activations of Bcl-2, Bcl-xl proteins and suppressed the expressions of Bad, Bax proteins caused by ELF-EMF exposure. In conclusion, these findings revealed that LSPCs protected against ELF-EMF-induced neurotoxicity through inhibiting oxidative stress and mitochondrial apoptotic pathway.